1. Field of the Invention
The present invention relates generally to polyimides which are suitable for high temperature applications as a result of their high or nondetectable glass transition temperature and their high thermooxidative stabilities. It relates particularly to three series or types of polyimides which are prepared from maleimide-acetylene terminated monomers.
2. Description of Related Art
Polyimides that are prepared from the reaction of organic compounds containing pendant acetylene groups or organic oligomers containing pendant acetylene groups are well known for their thermooxidative stability and exceptionally high glass transition temperatures. Likewise, organic compounds or oligomers containing activated carbon-carbon double bonds can be used to prepare polymers which are thermally stable if these compounds or oligomers contain imide moieties (i.e. maleimides).
However, polymers prepared from these compounds are often brittle and difficult to process. Bilow et al. (U.S. Pat. No. 4,108,836) developed a process for preparing alcohol soluble polyimide precursors which can be imidized in situ and cured through acetylene end groups. In a later invention, Bilow et al. (U.S. Pat. No. 4,276,407) invented a phenylacetylene terminated oligomer which melts at low temperatures. Grimes and Reinhart (U.S. Pat. No. 4,365,034) patented a new composition of matter comprising an acetylene-terminated polyimide oligomer and a cure rate inhibitor. Bilow et al. (U.S. Pat. No. 3,879,349) prepared polyimide polymers from the homopolymerization of acetylene substituted polyimide oligomers which could be processed into useful articles at moderate temperatures and pressures.